Molality Calculator
Find the molality of a solution in moles of solute per kilogram of solvent. Enter the moles directly, or give a mass and molar mass to work out the moles first, then add the mass of solvent in kilograms.
How to calculate molality
- Enter the moles of solute, or a mass with its molar mass to derive moles.
- Enter the mass of solvent in kilograms, not the mass of solution.
- Read the molality, computed from b = moles of solute / kg of solvent.
Examples
From moles and solvent
2 mol in 0.5 kg
4 mol/kg
From mass and molar mass
58.44 g NaCl (MM 58.44) in 1 kg
1 mol/kg
Frequently asked questions
What is molality?
Molality is the concentration of a solution measured in moles of solute per kilogram of solvent, written mol/kg or with the symbol m.
What is the molality formula?
Molality equals the moles of solute divided by the mass of solvent in kilograms, b = n / m. The solvent mass is used, not the total solution mass.
How is molality different from molarity?
Molality uses the mass of solvent in kilograms, while molarity uses the volume of solution in litres. Molality does not change with temperature.
How do I find moles from a mass?
Divide the mass in grams by the molar mass in grams per mole. This tool does that for you when you enter both a mass and a molar mass.
How do I convert grams of solvent to kilograms?
Divide the grams by 1000. For example 250 g of water is 0.25 kg. Enter that kilogram value into the solvent field.
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